Saturated hydraulic conductivity as an indicator of structural degradation in clayey soils of Ottawa area, Canada

Abstract Marked differences in soil structure and saturated hydraulic conductivity ( Ksat ) of fields of a clay soil in the Ottawa Valley were attributable to cropping systems. Ksat was estimated from morphology, and checked by measurement, at regularly-spaced points along transects through fields. Continuous corn ( Zea mays L.) culture for 5 years or more usually produced marked compaction of the lower part (10–25 cm depth) of the Ap horizon. Such compaction was associated with low Ksat , commonly less than 1 μ m s −1 . Comparable horizons of soils of the same series in hayfields (mixed grasses and legumes), on the other hand, had Ksat values ranging from approximately 10 to more than 100 times higher. Structure degradation of upper B horizons in long-term corn fields varied from slight to severe, but lower B horizons (below 50 cm) were not appreciably affected. At sites for which yield data of corn were available, shallow root growth and severely reduced (50% ) yields were associated with severe compaction and low Ksat . The results demonstrate that soil structure degradation can be assessed simply and reliably by observing morphology and estimating Ksat of horizons to a depth of 30–50 cm.